1. Field of the Invention
The present invention relates to a heat-assisted magnetic recording medium used in hard disk drives (HDD) and the like, and a magnetic recording and reading apparatus using the same.
Priority is claimed on Japanese Patent Application No. 2012-019185, filed on Jan. 31, 2012, the content of which is incorporated herein by reference.
2. Description of Related Art
In recent years, heat-assisted recording in which near-field light or the like is radiated to a magnetic recording medium so as to locally heat the surface and decrease the coercive force of the magnetic recording medium, thereby performing writing has been attracting attention as a next-generation recording method in which a 1 Tbit/inch2 class of surface recording density can be realized.
In a case in which the heat-assisted recording is used, it is possible to readily perform writing using a recording field of a current head even in a magnetic recording medium having a coercive force of several tens of kOe at room temperature. Therefore, in a heat-assisted magnetic recording medium, it becomes possible to use a material having a high crystal magnetic anisotropy (Ku) at a level of 106 J/m3 for a magnetic layer, and it is possible to miniaturize the diameter of magnetic grains to 6 nm or less while maintaining thermal stability. Known examples of the high Ku material include a FePt alloy having a L10-type crystal structure (Ku: approximately 7×106 J/m3), a CoPt alloy having a L10-type crystal structure (Ku: approximately 5×106 J/m3), and the like.
However, in order to order a FePt alloy so as to obtain an L10 structure, it is necessary to increase the substrate temperature to 600° C. or higher. However, the substrate temperature is desirably set to approximately 600° C. or less from the viewpoint of the heat resistance of a glass substrate. The ordering temperature can be decreased by adding a third element to FePt. For example, Appl. Phys. Lett. 80, 2147 (2002) describes that the ordering temperature can be significantly decreased by adding Cu to FePt. In addition, J. Appl. Phys. 92, 6104 (2002) describes that the ordering temperature can be decreased by adding Ag and Au in addition to Cu.